Eating Processed Junk Food Makes You Fat and Lazy, Study Suggests

by DailyHealthPost Editorial

burger and fries

What you eat affects everything about you: energy level, mood, how you look, and overall health. If you pay attention, you can actually notice a difference in how you feel after you eat certain foods.


Caffeine is obvious. Sugar is more complex: first we feel full of energy—zippy—then we crash and feel lethargic and weak. Of course, this leads to us wanting more sugar to bring up the energy level.

A vicious cycle, there are other ramifications we may instinctively know but don’t openly recognize: a recent study from UCLA (University of California at Los Angeles) demonstrates that a diet high in sugar makes us unmotivated and lazy.


Detrimental Effects of Junk Food

processed snacks

Many studies have linked eating sugar to weight gain and increased risk for cardiovascular disease and cancer. Others connect sugar to neurological impairment, including cognitive decline.

The new study reflects a nuance of the effects of sugar that wasn’t really documented before. Exploring the “chicken-and-egg” conundrum of obesity and associated conditions (depression, fatigue, lack of motivation), the question under scrutiny was whether obesity causes these consequences or the other way around? Scientists sought to discover the impact of processed versus unprocessed foods on cognition.


Two groups of rats were fed different diets: one low in fat but high in processed, simple carbohydrates (sugar) and the other a healthy, balanced rat diet of unprocessed foods that included complex carbohydrates. What the study found was that, after three months, there was a noticeable difference between the two groups—the rats on the low-fat, high-sugar diet were progressively gaining more weight.

After a While, The Reward isn’t Worth the Effort.

junk food study rats

Six months into the study, all rats were trained to push a lever to get a spoonful of sugar water. The number of lever presses to receive the treat was gradually increased, making the work to receive the reward more difficult.

Rats in both groups began to slow as the task got harder, taking breaks between pushing the lever, with some giving up completely. Starting with the same energy level, however, rats in the obese group took more frequent and longer breaks and gave up twice as fast as the rats on the non-processed diet.


Researchers then switched the diets of the two groups. The rats in the original processed-food group didn’t lose weight or show improvement in the lever-pressing task. This observation led to the theory that a diet of processed foods has a direct effect on the chemistry of the brain that isn’t quickly reversed and is manifested through lethargy.

To test the “chicken-and-egg” theory, the scientists changed the sugar water to plain water. In this way, they could see if motivation was linked to just sugar intake. They found that the obese rats on the junk food diet showed less motivation for water even when thirst was induced. All this testing is significant:

“rats are a great animal model for humans because there is so much overlap in the systems that regulate appetite and metabolism.”


What this means for us is that we are now aware of another side effect of a diet with a high processed-food content.

“Impaired Motivation”

Adding insult to injury, in addition to gaining weight, contracting serious disease, becoming depressed, affecting memory and cognition, and feeling all-around crummy, processed foods make us not care about any of that.

“Diet-induced obesity produces a substantial deficit in motivated behavior in rats, independent of dietary fat content. This holds implications for an association between obesity and motivation. Specifically, behavioral traits comorbid with obesity, such as depression and fatigue, may be effects of obesity rather than contributing causes. To the degree that refined foods contribute to obesity, as demonstrated in our study, they may play a significant contributing role to other behavioral and cognitive disorders.”


Healthy Foods You Should Eat.

healthy foods to eat